1. Field of the Invention:
The invention relates in general to escalators, and more specifically to escalators which have one or more drive units mounted in a supporting truss for engagement with a conveyor unit which carries escalator steps.
2. Description of the Prior Art:
U.S. Pat. Nos. 3,677,388; 3,682,289 and 3,707,220, all assigned to the same assignee as the present application, disclose new and improved passenger conveyor apparatus, such as escalators, in which the steps are pulled up the incline by toothed step links. A modular drive unit located in the truss, between the load bearing and return runs, just below the transition between the inclined portion and the upper horizontal portion of the escalator, includes a drive chain which engages toothed step links on an endless belt, on both the upper load bearing run and the lower return run. Additional drive units are added to the inclined portion, as required by the total rise.
The endless belt includes two sides, each of which are formed by pivotally interconnected, toothed step links. Step axles interconnect the two sides of the endless belt, and the steps are clamped to the step axles. The endless belt and steps are guided through the load bearing and return runs, as well as through the turnarounds which interconnect the load bearing and return runs, by axle rollers or guide wheels on the ends of the step axles, trailer wheels on the steps, and separate guide tracks for supporting the guide wheels and the trailer wheels.
The escalator construction of the hereinbefore mentioned patents provides many advantages over escalators which utilize a step chain and a top sprocket-drive machine to pull the steps up the incline. One of the most significant advantages is a substantial reduction in load on the working parts. As the length of the rise increases, the load on the parts remains low, with additional modular drive units being added to the incline, as required. The rigid step links maintain a constant distance between the step axles, eliminating the need for tensioning devices, which are required with the step chain construction.
For minimal wear of the drive chains, and proper load sharing between multiple drive units, each drive unit must be correctly aligned with the conveyor, and multiple drive units must be correctly spaced. If the axis of the drive unit which is oriented in the direction of the step travel direction is called the X-axis, the transverse axis is called the Y-axis, and the axis transverse to the plane which includes the X- and Y- axes is the Z-axis, each drive unit must be correctly oriented about its X-, Y-, and Z-axes such that the X-axis of the drive unit is parallel with the longitudinal axis of the supporting truss, and the toothed links on each side of the endless belt or conveyor make like contact with drive chains located on each side of the drive unit. Each drive unit must be adjustable in the direction of its Z-axis to provide the desired tooth-drive chain contact, and in the direction of its X-axis to properly engage the toothed links with the drive chain across the load range. The latter adjustment is especially important when more than one drive unit is used to drive the conveyor, as it is this adjustment which causes the drive units to properly share the load across the load range. Co-pending Application Ser. No. 292,974, filed Sept. 14, 1981, entitled "Method of And Apparatus for Positioning the Drive Units of a Plural Drive Escalator", now U.S. Pat. 4,397,096, which is assigned to the same assignee as the present application, describes the importance of precise drive spacing in more detail.
Thus, it is desirable to be able to quickly and accurately position each drive unit in the truss.
In addition to being able to quickly and easily select the desired drive position, it is important that the selected position be maintained as the drive unit is loaded. The toothed link-drive chain interface introduces forces into the drive sprockets which transfer the forces through the drive mounting frame or base to the supporting truss. These forces can cause bending moments to be applied to various elements of the drive mounting base, causing harmful deflection and misalignment of the driving and rotating elements of the drive unit. Thus, it would be desirable to provide a drive unit-truss construction which minimizes deflection of these critical elements of the drive unit.